A fold knife has become a common tool in the daily life, bringing about great convenience for people. The existing folding knifes can be classified into a manual type fold knife and a semi-automatic type fold knife. Just as the name implies, the manual type fold knife needs to be operated by a user's hand throughout its whole opening procedure, whereas as for the semi-automatic fold knife, the user only needs to exert a force at the beginning stage of the opening while in the sequential stage the fold knife is automatically opened by means of a device inside the knife.
It is appreciated from the above that since the user needs to operate the manual fold knife throughout the whole opening procedure, it needs a great effort to open it but on the other hand it is comparatively safe to use for the users such as kids. Contrarily, the semi-automatic fold knife can be facilitated in opening while degraded in terms of safety. As a result, there is a need of a fold knife capable of switching between the manual operation condition and the semi-automatic operation condition depending on the requirements of a user.